A YEAST ARTIFICIAL CHROMOSOME (YAC) LIBRARY CONTAINING 10 HAPLOID CHICKEN GENOME EQUIVALENTS

We report the construction of a YAC library that provides 10-fold redu ndant coverage of the chicken genome. The library was made by transfor ming S. cerevisiae AB1380 with YAC constructs consisting of partially digested and size fractionated (>465 kb) EcoRI genomic fragments ligat ed to pCGS966 YAC vector arms. The primary library provides 8.5-fold r edundant coverage and consists of 16,000 clones arrayed in duplicate 9 6-well microtiter plates and gridded on nylon membranes at high densit y (18,000 clones/484cm(2)). The average insert size, 634 kb, was deriv ed from size fractionation of a random sample of 218 YACs. Hybridizati on of five unlinked chicken genes to colony blots revealed six or more positive clones. This is consistent with the theoretical expectation from average insert sizes and number of clones. A second collection of clones consists of a further 20,000 colonies, of which 20% contain in serts larger than 450 kb and 80% contain only coligated vector arms. W e estimate that these clones provide a further 1.5-fold redundant cove rage of the chicken genome; thus, the total collection of 36,000 clone s provides 10-fold redundant coverage of the chicken genome. The libra ry is intended as a resource for fine-scale analysis of the organizati on of the chicken genome and is presently being used to construct a co ntig map of chicken Chromosome (Chr) 16, which contains the MHC and nu cleolar organizer.